System and method for establishing relative distance and position of a transmitting antenna

ABSTRACT

A system and method for a second wireless device to establish distance and location of a first device which is transmitting radio waves includes the first and second devices. Each second device includes two or more (N in number) receiving antennas. An angle between the directions in which adjacent receiving antennas receive the strongest signals is 360°/N. The second device obtains a received signal strength indicator (RSSI) of each receiving antenna receiving signals from the first device, and from the two strongest receiving antennas, calculation of an angle between the first device and one of the adjacent receiving antennas can be performed. The distance between the first device and the second device can also be calculated.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of pending U.S. patent applicationSer. No. 16/412,826, filed on May 15, 2019 and entitled “SYSTEM ANDMETHOD FOR ESTABLISHING RELATIVE DISTANCE AND POSITION OF A TRANSMITTINGANTENNA”, the contents of which are incorporated by reference herein.

FIELD

The subject matter herein generally relates to wireless communications.

BACKGROUND

Most methods require multiple nodes or devices in a particularplacement, this is costly and difficult to apply to ordinary homeenvironments. In addition, WIFI access points and Internet of Things(IOT) mostly use dipole antennas to transmit and receive signals, andthen position by means of beam forming. However, such positioningmethods are susceptible to environmental interference and negativelyaffect positioning accuracy.

Therefore, there is room for improvement within the art.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present disclosure will now be described, by wayof embodiment, with reference to the attached figures.

FIG. 1 is a system architecture of one embodiment of a positioningsystem for antennas used indoors.

FIG. 2 is a schematic view of signals of antennas of the positioningsystem of FIG. 1.

FIG. 3 is a flow chart of one embodiment of a positioning method forantennas used indoors.

FIG. 4 is schematic view of a pattern of one of the receiving antennasof the positioning system of FIG. 1.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale and the proportions of certain parts havebeen exaggerated to better illustrate details and features of thepresent disclosure.

Several definitions that apply throughout this disclosure will now bepresented.

The term “substantially” is defined to be essentially conforming to theparticular dimension, shape, or other feature that the term modifies,such that the component need not be exact. For example, “substantiallycylindrical” means that the object resembles a cylinder, but can haveone or more deviations from a true cylinder. The term “comprising” whenutilized, means “including, but not necessarily limited to”; itspecifically indicates open-ended inclusion or membership in theso-described combination, group, series, and the like.

The present disclosure is described in relation to a positioning systemand method for antennas.

FIG. 1 shows a system architecture of one embodiment of a positioningsystem. The positioning system includes a first device 1 and a pluralityof second devices 2. The system architecture can be implemented in abuilding such as a shopping mall, a factory, a hospital, a hotel, arestaurant, an airport, and the like. The first device 1 can determinethe position of each second device 2. In this embodiment, the firstdevice 1 determining the position of one second device 2 is taken as anexample for description.

In this embodiment, the first device 1 can be a router or other accesspoint. The plurality of second devices 2 can be wireless communicationdevices having a transceiving function. In this embodiment, the seconddevice 2 and the first device 1 may also be wirelessly connected. Thewireless communication protocols include, but are not limited to, forexample, WIFI and ZIGBEE.

The first device 1 comprises a plurality of transmitting antennas(transmitting antenna TX) and at least two receiving antennas. In thisembodiment, each transmitting antenna TX is a dipole antenna with a gainof less than 6 dB, and each receiving antenna is a directional antenna.In this embodiment, four receiving antennas of the first device 1 aretaken as an example for description. The four receiving antennasincludes a first receiving antenna RX1, a second receiving antenna RX2,a third receiving antenna RX3, and a fourth receiving antenna RX4. Anumber of the transmitting antennas TX is also four. The four receivingantennas and four transmitting antennas are evenly and alternatelyarranged. In the positioning system of the present disclosure, afterseparately arranging the transmitting antennas TX and the receivingantennas, the directional antennas are used as the receiving antennas,and a beam forming to improve online communication quality can be usedto communicate with the second device 2.

Referring to FIG. 2, each receiving antenna has a direction in whichintensity of a received signal is strongest. For example, the directionin which the first receiving antenna RX1 receives a strongest signal isA1, and the direction in which the fourth receiving antenna RX4 receivesa strongest signal is A4. An angle θ between the directions in whichadjacent receiving antennas receive the strongest signals is the same,that is 360°/N. In 360°/N, N is the number of receiving antennas RX. Inan embodiment, the number of the receiving antennas RX is four (i.e.N=4), therefore 0=90°. Thus, the angle θ between the directions A1 andA4, the directions in which the first receiving antenna RX1 and thefourth receiving antenna RX4 receive the strongest signals, is 90°. Inother embodiments, N may be equal to 2, 3, 5-10, etc. One skilled in theart can arrange a suitable number of receiving antennas RX according tohardware requirements and space around a device. In this embodiment, aspace in which the first device 1 is located may be divided into fourquadrants according to the intensities of the received signals of thefour receiving antennas RX. The four quadrants are a first quadrantRXQ-I, a second quadrant RXQ-II, a third quadrant RXQ-III, and a fourthquadrant RXQ-IV. Each quadrant is a region where a certain receivingantenna RX receives stronger signals than do other receiving antennasRX.

FIG. 3 is a flow chart of an embodiment of a positioning method. Thepositioning method includes the following steps:

Block S10, the first device 1 waits for a connection with the seconddevice 2 after being powered on.

Block S11, the first device 1 establishes the connection with the seconddevice 2, and receives signals transmitted by the second device 2.

Block S12, the first device 1 obtains a received signal strengthindicator (RSSI) of each receiving antenna receiving signals from thesecond device 2. For example, in this embodiment, the RSSI of the firstreceiving antenna RX1 is AntI_(RSSI), d the RSSI of the fourth receivingantenna RX4 is AntI_(RSSI). In this embodiment, the first device 1 usestime division multiplexing to calculate the RSSI of each receivingantenna from the second device 2, even if the first device 1 has onlyone feeding point. The positioning system can still achieve the samepositioning effect by using the time division multiplexing way.

In this embodiment, the Block S11 includes the following sub-steps:

Block S120, according to the obtained RSSI, an average value of the RSSIbeing received a preset number of times in respect of each receivingantenna receiving signals from the second device 2 (for example, lastfive signals received) is used as the RSSI of each receiving antenna.

Block S121, the first device 1 determines whether the RSSI of eachreceiving antenna remains equal to the average value of the RSSI. If theRSSI of each receiving antenna is equal to the average value, theprocess returns to block S110, but if the RSSI of each receiving antennaRX is not the average value, the process goes to block S13.

Block S13, the first device 1 determines upon two receiving antennaspositioned closest to the second device 2. In this embodiment, the firstdevice 1 selects two receiving antennas of maximum RSSI, and determinesa position of the second device 2 relative to the first device 1,according to the two maximum RSSIs. For example, if the RSSIs of thefirst receiving antenna RX1 and the fourth receiving antenna RX4 are thetwo maximum RSSIs, the first device 1 determines that the firstreceiving antenna RX1 and the fourth receiving antenna RX4 are closestto the second device 2, and that the second device 2 is located in thefirst quadrant RXQ-I between the first receiving antenna RX1 and thefourth receiving antenna RX4.

Block S14, the first device 1 calculates an angle between the seconddevice 2 and one of the closest receiving antennas. In this embodiment,angle θ1 between the second device 2 and the first receiving antenna RX1and angle θ4 between the second device 2 and the fourth receivingantenna RX4 are calculated.

Referring to FIG. 4, in this embodiment, assuming that pattern of thereceiving antennas is uniform, a gain Gt of the receiving antenna can becalculated by

${{Gt} = \frac{AS}{AAP}},$

the following formula, wherein, AS represents a circular area, and AAPrepresents a sector (a cross-section) of that area.

A model of the receiving antenna RX is substantially a rectangular area,and a long side a and a short side b of the rectangular area arecalculated by the formulas a=γ sin θ and b=γ sin φ. Thus, thecross-sectional area AAP is equal to γ² sin θ sin ϕ. The gain Gt of thereceiving antenna can be calculated by the formula

${Gt} = {\frac{AS}{AAP} = {\frac{4{\pi\gamma}^{2}}{\gamma^{2}\sin\;{\theta sin\varphi}} = {\frac{4\pi}{\sin\;{\theta sin\varphi}}.}}}$

In addition, assuming that the cross-sectional area is square, θ×φsubstantially. Thus, the gain Gt of the receiving antenna RX can befurther calculated by the formula

${{G(t)} = \frac{4\pi}{\sin^{2}\theta}}.$

Since the first quadrant RXQ-I and the second quadrant RXQ-IV areperpendicular to each other, it can be considered that θ4=90°−θ1. Thus,the gains of the first receiving antenna RX1 and the fourth receivingantenna RX4 can be respectively indicated by the formulas

${{Gt}\; 1({dB})} = {{10{\log\left( \frac{4\pi}{\sin^{2}\theta 1} \right)}\mspace{14mu}{and}\mspace{14mu}{Gt}\; 4({dB})} = {10{{\log\left( \frac{4\pi}{\cos^{2}\theta 1} \right)}.}}}$

Substituting

${{Gt}\; 1({dB})} = {{10{\log\left( \frac{4\pi}{\sin^{2}\theta 1} \right)}\mspace{14mu}{and}\mspace{14mu}{Gt}\; 4({dB})} = {10{\log\left( \frac{4\pi}{\cos^{2}\theta 1} \right)}}}$

into the signal intensity formula of the receiving antennas,AntI_(RssI)=Pt+Gt(θ)+Gr+20 log λ−20 log d, wherein, Pt represents anoutput power of the second device 2, Gr represents a gain of thetransmitting antenna, d represents a distance between the second device2 and the first device 1, λ represents a wavelength. The formula

${{AntI}_{RSSI} - {AntIV}_{RSSI}} = {{{{Gt}\; 1({dB})} - {{Gt}\; 4({dB})}} = {10{\log\left( \frac{\cos^{2}\theta 1}{\sin^{2}\theta 1} \right)}}}$

can be obtained.

It can be further obtained that

${\theta 1} = {\frac{1}{2}{{\cos^{- 1}\left( {\frac{1}{{{In}\left( \frac{{AntI}_{RSSI} - {AntIV}_{R}}{10} \right)} + 1} - 1} \right)}.}}$

The angle θ1 between the second device 2 and the first receiving antennaRX1 can thus be calculated.

Block S14, the first device 1 calculates the distance between the seconddevice 2 and the first device 1.

In this embodiment, the gain Gt1 (dB) of the first receiving antenna RX1is calculated according to the formula

${{Gt}\; 1({dB})} = {10{{\log\left( \frac{4\pi}{\sin^{2}\theta 1} \right)}.}}$

According to the formula AntI_(RssI)=Pt+Gt(θ)+Gr+20 log λ−20 log d, theformula

$d = {\frac{1}{20}{{In}\left( {{AntI}_{RSSI} + {Pt} + {G{t(\theta)}} + {Gr} + {20\log\;\lambda}} \right)}}$

can be derived. Since Pt, Gr, and 20 log λ can be known according toproduct information of the first device 1 and the second device 2, thedistance d between the first devices 1 and the second device 2 can becalculated thereby achieving the position of the second device 2.

In other embodiment, the positioning system can include multiple seconddevices 2, the positioning method further includes:

Block S15, the first device 1 identifies the second device 2 accordingto physical information of the second device 2, such as a MAC address,and determines respective positions of second devices 2 according to themethod described in blocks S10 to S14.

In other embodiment, when the number of the receiving antennas is N, theangle between the directions of the strongest received signals betweenadjacent receiving antennas is 360°/N (i.e.

$\left. {{\theta 4} = {\frac{360{^\circ}}{N} - {\theta 1}}} \right).$

Substituting

${\theta 4} = {\frac{360{^\circ}}{N} - {\theta 1}}$

into the formulas in blocks S14, the formula

${{AntI}_{RSSI} - {AntIV}_{RSSI}} = {{{{Gt}\; 1({dB})} - {{Gt}\; 4({dB})}} = {{10{\log\left( \frac{4\pi}{\sin^{2}\theta 1} \right)}} - {10{\log\left( \frac{4\pi}{\sin^{2}\left( {\frac{360{^\circ}}{N} - {\theta 1}} \right)} \right)}}}}$

is obtained to calculate the angle θ1 between the second device 2 andthe first receiving antenna RX1. Furthermore, combining with the formulaAntI_(RssI)=Pt+Gt(θ)+Gr+20 log λ−20 log d, the distance d between thesecond device 2 and the first device 1 can be calculated.

Therefore, if the number of receiving antennas is increased, thepositions of all second devices 2 can be determined more accuratelyusing the positioning method of the present disclosure. Receivingantennas with different antenna gains and different positioning anglescan be established once the positioning angles satisfy the abovecondition (i.e. the angle between the directions of the strongestreceived signals between adjacent receiving antennas is 360°/N).

The positioning system and method of the present disclosure calculatesthe angle between the second device 2 and one receiving antenna, andcalculates the distance between the first device 1 and the second device2 according to such angle. The position of a second device 2 can thus bedetermined by the receiving antennas. The present disclosure only needsone first device 1 and the positioning method as the core architectureof the entire positioning system, and does not require additional costto achieve positioning. The system architecture is simple and the costis low. Meanwhile, the positioning process is not subject to significantinterference, and the positioning accuracy is high.

In other embodiment, the positioning system and method of the presentinvention can be used in indoor or outdoor models to improve theaccuracy of distance estimation.

In other embodiment, the positioning system of the present invention canbe widely applied to a single antenna communication device, for example,BLUETOOTH, wireless personal area network (ZIGBEE), and Internet ofThings (IOT), thereby more quickly determining a position or a distanceof an object to be tested (i.e. the second device 2). This can be forpractical applications such as a smoke detection and a sensor failuredetection, in an industrial or domestic environment. For example, whenthe positioning system is applied in the case of the smoke detection orthe sensor failure detection, the second device 2 being positioned inthe monitoring area, a smoke or sensor failure triggers thecorresponding second device 2 to establish a communication with thefirst device 1. The positioning method can be used to determine theposition of the second device 2. Thus, an accident or a place where thefailure occurs can be found rapidly, and effective measures can betaken.

The embodiments shown and described above are only examples. Manydetails are often found in the art such as the other features of theantenna structure and the wireless communication device. Therefore, manysuch details are neither shown nor described. Even though numerouscharacteristics and advantages of the present disclosure have been setforth in the foregoing description, together with details of thestructure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the details, especially inmatters of shape, size, and arrangement of the parts within theprinciples of the present disclosure, up to and including the fullextent established by the broad general meaning of the terms used in theclaims. It will therefore be appreciated that the embodiments describedabove may be modified within the scope of the claims.

What is claimed is:
 1. A positioning system comprising: a first devicecomprising two receiving antennas, wherein a number of the at least tworeceiving antennas is defined as N, an angle between the directions inwhich adjacent two of the receiving antennas receive the strongestsignals is 360°/N; and a second device having a transceiving function,wherein the first device obtains received signal strength indicators(RSSI) of the receiving antennas, determines which of the two receivingantennas is closest to the second device according to the receivedsignal strength indicators (RSSI), calculates an angle between thesecond device and the closest receiving antennas according to thereceived signal strength indicators (RSSI), and obtains a distancebetween the second device and the first device according to the angleand a gain of one of the closest receiving antennas.
 2. The positioningsystem of claim 1, wherein the first device further calculates the anglebetween the second device and the closest receiving antennas accordingto a following formula${{AntI}_{RSSI} - {AntIV}_{RSSI}} = {{10{\log\left( \frac{4\pi}{\sin^{2}\theta 1} \right)}} - {10{\log\left( \frac{4\pi}{\sin^{2}\left( {\frac{360{^\circ}}{N} - {\theta 1}} \right)} \right)}}}$wherein, θ1 represents the angle between the second device and theclosest receivings antenna, AntI_(RSSI) and AntIV_(RSSI) representsRSSIs of the two closest receiving antennas.
 3. The positioning systemof claim 2, wherein the first device calculates the gain of one of theclosest receiving antennas according to a following formula${{{Gt}\; 1({dB})} = {10{\log\left( \frac{4\pi}{\sin^{2}\theta 1} \right)}}},$wherein Gt1(θ1) represents the gain of the closest receiving antennas,the first device further calculates the distance between the seconddevice and the first device according to a following formula${{d\; 1} = {\frac{1}{20}\ln\;\left( {{AntI}_{RSSI} + {Pt} + {G{t\left( {\theta 1} \right)}} + {Gr} + {20\log\;\lambda}} \right)}},$wherein Pt represents an output power of the second device, Grrepresents a gain of a transmitting antennas and λ represents awavelength.
 4. The positioning system of claim 3, wherein the firstdevice obtains a preset number of RSSIs of each of the receivingantennas, and uses an average value of the RSSIs as the RSSI of each ofthe receiving antennas.
 5. The positioning system of claim 1, whereinthe first device identifies the second device according to physicalinformation of the second device and the physical information is a MediaAccess Control (MAC) address.
 6. The positioning system of claim 1,wherein N is equal to four, an angle between the directions of thestrongest received signals between adjacent receiving antennas is 90°,the first device calculates the angle between the second device and theclosest receiving antennas according to a following formula${{\theta 1} = {\frac{1}{2}{\cos^{- 1}\left( {\frac{1}{{{In}\left( \frac{{AntI}_{RSSI} - {AntIV}_{RSSI}}{10} \right)} + 1} - 1} \right)}}},$wherein, θ1 represents the angle between the second device and theclosest receiving antennas, AntI_(RSSI) and AntIV_(RSSI) representsRSSIs of the two closest receiving antennas.
 7. A positioning method,applicable in a first device to determine a distance between a the firstdevice and a second device, the first device comprising at least tworeceiving antennas, a number of the receiving antennas is defined as N,an angle between the directions in which adjacent two of the receivingantennas receive the strongest signals is 360°/N, the second devicehaving a transceiving function, the positioning method comprising: (a)establishing a connection between the first device and the seconddevice; (b) obtaining received signal strength indicators (RSSI) of thereceiving antennas received signals from the second device; (c)determining which of the two receiving antennas is positioned closest tothe second device according to received signal strength indicators(RSSI); and (d) obtaining an angle between the second device and theclosest receiving antennas according to the received signal strengthindicators (RSSI), and calculating a distance between the second deviceand the first device according to the angle and a gain of one of theclosest receiving antennas.
 8. The positioning method of claim 7,wherein the step (d) comprises: calculating the angle between the seconddevice and the closest receiving antennas according to a followingformula${{{AntI}_{RSSI} - {AntIV}_{RSSI}} = {{10\mspace{14mu}{\log\left( \frac{4\pi}{\sin^{2}\theta 1} \right)}} - {10\mspace{14mu}{\log\left( \frac{4\pi}{\sin^{2}\left( {\frac{360{^\circ}}{N} - {\theta 1}} \right)} \right)}}}},$wherein, θ1 represents the angle between the second device and theclosest receiving antennas, AntI_(RSSI) and AntIV_(RSSI) representsRSSIs of the two a closest receiving antennas.
 9. The positioning methodof claim 8, wherein the step (d) comprises: calculating a gain of one ofthe closest receiving antennas according to a following formula${{{Gt}\; 1({dB})} = {10\mspace{14mu}{\log\left( \frac{4\pi}{\sin^{2}\theta 1} \right)}}},$wherein Gt1(θ1) represents the gain of one of the closest receivingantennas; calculating a distance between the second device and the firstdevice according to a following formula${{d\; 1} = {\frac{1}{20}{\ln\left( {{AntI}_{RSSI} + {Pt} + {{Gt}({\theta 1})} + {Gr} + {20\mspace{14mu}\log\;\lambda}} \right)}}},$wherein Pt represents an output power of the second device, Grrepresents a gain of a transmitting antenna, and λ represents awavelength.
 10. The positioning method of claim 7, wherein the step (a)comprises: obtaining a preset number of RSSIs of the receiving antenna,and using an average value of the RSSIs as the RSSI of the receivingantenna.
 11. The positioning method of claim 7, further comprising:identifying the second device according to physical information of thesecond device, wherein the physical information is a Media AccessControl (MAC) address.
 12. The positioning method of claim 7, wherein Nis equal to four, an angle between the directions of the strongestreceived signals between the adjacent receiving antennas is 90°, thestep (a) comprises: calculating the angle between the second device andthe closest receiving antenna according to a following formula${{\theta 1} = {\frac{1}{2}{\cos^{- 1}\left( {\frac{1}{{{In}\left( \frac{{AntI}_{RSSI} - {AntIV}_{RSSI}}{10} \right)} + 1} - 1} \right)}}},$wherein, θ1 represents the angle between the second device and theclosest receiving antennas, AntI_(RSSI) and AntIV_(RSSI) representsRSSIs of the two closest receiving antennas.
 13. A positioning systemcomprising: a first device comprising two receiving antennas; and asecond device having a transceiving function, wherein the first deviceobtains received signal strength indicators (RSSI) of the receivingantennas, determines which of the two receiving antennas is closest tothe second device according to the received signal strength indicators(RSSI), calculates an angle between the second device and the closestreceiving antennas according to the received signal strength indicators(RSSI), and obtains a distance between the second device and the firstdevice according to the angle.
 14. The positioning system of claim 13,wherein the first device obtains the distance between the second deviceand the first device further according to a gain of one of the closestreceiving antennas.
 15. The positioning system of claim 13, wherein thefirst device obtains the distance between the second device and thefirst device further according to an output power of the second device.16. The positioning system of claim 13, wherein the first device obtainsthe distance between the second device and the first device furtheraccording to a gain of a transmitting antenna.